I can see this being useful even with racing. I know most of the time in online racing the start grid is all messed up and doesn't seem to be based on qualifying laps at all, so we end up spending a lap getting into the right order and then puttering around the track, when we complete that lap the race begins. Cruise control would definitely make that first lap more organized host would just have to say "set cruise control to X mph" and then you just get around the course that way rather than constantly trying to hold a low speed, hoping you're not messing up the person behind, and getting messed up by the person in front.
Blinkers would also be extremely useful in races as well.